342 LEISURE-TIME STUDIES. 



building the nest ; they close and open the doors of the 

 hive ; but their chief office appears to be that of hunting for 

 plant-lice. In England, on the contrary, the slaves are 

 strictly household servants, rarely venturing out of doors. 

 Such differences depend most probably on the fact that a 

 greater number of slaves occur in Swiss than in English 

 nests, and they may therefore be employed in a wider range 

 of duties on the Continent than at home. A fewer number 

 of slaves, a greater aptitude on the part of the slaves for 

 their duties, the inability of the masters to perform the 

 duties of the slaves, each or all of these causes combined 

 would serve to increase the value of the servitors, and at the 

 same time to reduce the independence of the masters. 



This increase of the value of the slaves as active factors 

 in the ant community, might at length proceed to such ex- 

 tremes as we see exemplified in the Polyergtts, already 

 referred to, a race which has become literally unable to feed 

 itself, and to discharge the simplest duties of ant existence, 

 and whose actual life is entirely spent in marauding expe- 

 ditions on the nests of its neighbours. 



The subject of the general intelligence of ants, and of 

 their ability to adapt themselves to awkward and unusual cir- 

 cumstances, may be briefly touched upon by way of conclusion. 

 Between the reason and intelligence of higher animals 

 and the " instinct" of ants there is unquestionably a great 

 gulf fixed. I make this statement unhesitatingly, notwith- 

 standing that I should no more willingly attempt to define 

 "instinct" than to give an exact definition of "insanity." 

 In the latter case one may make the definition so limited, 

 as practically to exclude all save one class of cases, or so 

 wide as to include even the judge on the bench. In the case 

 of instinct, the rigid definition of one authority might cause 

 us to regard it as the exclusive property of lower forms and 

 as having no relationship whatever with the mental powers 

 of higher beings ; or, on the other hand, as being but a modi- 

 fied form of, or in some respects identical with, these very 

 powers. We know too little respecting the so-called " auto- 



